Snap acting thermal element



y 28, 1968 J. M. ALGINO 3,386,065

SNAP AC'I ING THERMAL ELEMENT Filed March 15, 1967 2 Sheets-Sheet 2 F 49 6 0 xv I v J-Lz 7 mi W" ii /l "WW @5 72 7/ INVENTOR. JOSEPH M '44G/A/O C Q I a ATTORNEYS United States Patent 3,386,065 SNAP ACTINGTHERMAL ELEMENT Joseph M. Algino, Niles, Ill., assignor to The DoleValve Company, Morton Grove, 11]., a corporation of Illinois Filed Mar.15, 1967, Ser. No. 623,440 12 Claims. (Cl. 337-315) ABSTRACT OF THEDISCLOSURE A thermal power unit having a base cup and a guide membersecured to the base cup to form a cavity therebetween and having athermally expansible substance within the cavity and a resilient squeezetype boot displaced between the thermally expansible substance and theguide portion. The boot has an opening for receiving a power piston andthe expansion of the thermally expansible substance compresses the bootto cause the power piston to extend therefrom. A detent groove 1s formedabout the power member piston in the vicinity of the guide member and aresilient catch means is biased into engagement with the detent grooveto convert the otherwise smooth extension of the piston into a snapaction motion.

BACKGROUND OF THE INVENTION Field of the invention An important featureof this invention is the provision of a thermal power unit having a cupmember and a resilient squeeze type boot operably disposed within thecup member for moving a piston relatively therefrom wherein the pistonhas an irregular surface portion engageable with a resilient catch meansto convert the otherwise smooth motion of the piston into a snap actionmotion.

Another feature of the invention is the provision of a snap acting powermember wherein the snap acting motion of the member is confined to aspecific temperature differential and to a specific piston traveldistance and wherein the motion of the piston outside of the specifiedtravel distance and temperature is a smooth steady motion.

An object of the invention is the provision of a thermal power unithaving a cup member and a guide member secured at out-turned flanges formaintaining a resilient squeeze type boot in position within the cupmember and wherein a detent groove is formed about the circumference ofthe power member piston in the vicinity of the guide member and whereina detent ball is spring biased into engagement with the detent groove tolimit the travel of the piston until a specific temperature level and,hence, a specific compression of the squeeze boot is reached.

Another object of this invention is to provide a thermally operatedpower member piston wherein the motion of the piston is abrupt over arelatively low temperature range and is steady as the temperatureincreases to points above the relatively low temperature range.

A still further object of this invention is to provide an improved meansfor temporarily loading a power piston of a thermal power unit duringthe extension of the piston from a resilient squeeze type boot as thetemperature ambient rises from a low level to a high level.

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Another object of this invention is to provide a leaf spring type switchhaving two blades mounted in a housing and having a thermal power unitalso mounted in the housing to move one of the blades out of contactwith the other blade and wherein a thermal power unit has a detentgroove formed about the power member piston thereof and wherein a detentball bearing is biased into engagement with the power piston to inhibitthe motion of the piston until a specified temperature is reached andthen to release the piston into a snap action travel for breaking thecontact between the switch blades.

A still further object of the invention is to provide a fluid controlvalve having an inlet and an outlet and a valve means disposed betweenthe inlet and the outlet and having a thermal power unit of the typedescribed above disposed in the valve housing so as to move the valvemeans into an open position by a snap acting motion and to close thevalve means by an initial snap motion and a subsequent slow closemotion.

Other and further objects of this invention will be apparent to thoseskilled in this art from the following detailed description and theannexed sheets of drawings which show several embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a sectional view through athermal power unit having the features of this invention andspecifically showing the positioning of the detent groove and the detentball bearing which is biased into engagement with the groove;

FIGURE 2 is a temperature versus travel graph showing the motion of aconventional power member piston;

FIGURE 3 is a graph similar in nature to the graph of FIGURE 2 andshowing the travel of a power member piston in response to changes intemperature ambient the thermally expansible wax and showing inparticular the presence of the snap action and its confinement to aspecific region of the piston travel;

FIGURE 4 is a sectional view of a leaf spring type switch having switchcontacts which are engaged and moved out of engagement by a power memberpiston similar to the piston shown in FIGURE 1; and

FIGURE 5 is a sectional view through a fluid control valve having avalve member which is opened and closed by a thermal power unitaccording to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermal power unit of thisinvention has a cup member 10 and a guide member 11. The cup member 10has a cylindrical side wall 11, a base Wall 12 and an out-turned annularflange 13. The side wall 11 and the base wall 12 form a cavity 14 whichcontains a thermally expansible pellet 15.

A resilient boot 16 which is disposed within the cavity 14 has a taperedwall portion 17 and a web portion 18. A bead 19 is formed at the outerperiphery of the web 18 as shown in FIGURE 1.

The boot 16 is held in position within the cavity 14 by the presence ofthe guide member 11 against the out turned flange 13 of the cup member10. In particular, the guide member 11 also has an out-turned flange 20which has a groove 21 formed at the outer perimeter thereof. The web 18is disposed between the flanges 13 and 20, and the flange 13 is spunover the flange 20 to securely grip the flanges in position and tocompress the web 18 between the flanges as shown.

The boot 16 has a further tapered wall portion 22 extending upwardlyfrom the web 18, and the guide member 11 has a surface 23 substantiallyconforming to the upper surface of the boot and preventing the movementof the boot upwardly from the cavity 14.

The resilient boot 16 has a central opening 24 formed therethrough, andlikewise the guide member 11 has a central opening 25 formed insubstantial alignment with the opening 24 of the boot. Therefore, apower member piston 26 may be disposed centrally through the opening 25and the opening 24 to seat at the lower surface 27 of the boot opening24.

Considering only the features of the thermal power unit of FIGURE 1which have been described to this point, it is apparent to those skilledin the art that the elevating of temperature about the cup member 11will heat the thermally expansible wax and compress the walls of theboot to sequeeze the piston 28 outwardly therefrom and upwardly throughthe Opening of the guide member 11. This motion would be substantiallyuniform and, due to the specific design of the boot 16 and the cupmember 11, the movement of the piston 26 will not be characterized bysharp abrupt motions but will be steady in response to temperature rise.

For instance, in FIGURE 2 the travel of the piston 26, as would beexpected from a conventional thermal power unit, is shown. Inparticular, the line 28 illustrates the amount of travel experienced bythe piston 26 in response to a given temperature rise measured along thehorizontal axis. Only when the point 29 is reached, at which the pistonis physically halted due to a stop member on the piston or the like,does the travel of the piston cease to be steady for increasingtemperature. The line 29, which corresponds to the travel of the pistonmeasured during a temperature decline, is also steady and is notcharacterized by abrupt piston motions.

However, in certain devices in which thermal power units are utilized,it is desirable to have the piston move abruptly during a specific timeor temperature interval and to move slowly at other time or temperatureintervals. Accordingly, the thermal power unit of this invention asshown in FIGURE 1 incorporates a means for conforming the travel of thepiston to an irregular desired motion temperature response.

The means to control the motion of the piston 26 in FIGURE 1 includes adetent groove 31 which is formed circumferentially about the piston inthe vicinity of the guide member 11 and a catch bore 32 which is formedsubstantially perpendicular to the guide bore 25 and which intersectsthe guide bore 25. The catch bore 32 has a detent ball bearing 33slideably mounted therein and has a coiled spring 34 disposed betweenthe ball 33 and a plug 35. The plug 35 is threadedly mounted within thecatch bore 32 such that by the use of a screwdriver or other suitabletool within the groove 36, the plug 35 may be advanced or retarded toincrease or decrease the compression of the coil spring 34. Essentially,the ball 33, together with the coil spring 34, places an axial loadingon the piston 26 so long as the groove 31 is aligned with the ball 33.After, however, the groove 31 is moved out of contact with the ball 33,the smooth surface of the piston 2-6 maintains the ball in a recessedposition within the catch bore 32, and the presence of the ball hassubstantially no effect on the subsequent motion of the piston.-

The axial loading of the piston 26 is accomplished either at the edge 37of the detent groove 31 or at the edge 38 thereof. During the upwardtravel of the piston 26, the ball 33 acts against the edge 37 to retardthe motion of the piston, and during the retraction motion of the piston26, the ball 33 acts against the edge 38 to retard the motion. Ofcourse, as soon as either of the edges 37 or 38 are moved past thecenter of the ball 33, the motion of the piston is then unaffected bythe presence of the ball 33.

Movement of a piston in a thermal power unit similar to the unit shownin FIGURE 1 is illustrated graphically in FIGURE 3. In particular, afirst line segment 39 illustrates the motion of the piston when thegroove 31 is closer to the boot 16 than the ball 33. At this time, thepresence of the ball does not affect the axial motion of the piston inresponse to temperature and accordingly the movement of the piston issubstantially uniform. However, at a point 40, the groove 31 engages theball 33 and a further axial movement of the piston is prohibited untilthe temperature rises to T2 at which time the travel of the pistonsuddenly snaps from the point 41 to the point 42. This snap action isgenerated due to the fact that while the piston is locked intoengagement with the ball 33, the wax is building up compression withinthe cavity 14 and the boot 16 is being compressed due to the extraloading on the piston 26 by the ball 33. When the ball 33 is releasedfrom engagement with the groove 31, the sudden decrease in loadingcauses the wax and boot to bounce upwardly to release the compressionthereof. This bounce is then responsible for the snap action of thepiston in moving from 41 to 42 in the graph of FIGURE 3. After themotion of the piston has been released from the engagement of the groove31 with the ball 33, the piston travels uniformly in the region 43. Atthe point 44, a stop means or the like engages the piston and preventsthe piston from further motion in response to temperature rise.

A similar effect occurs on a temperature decline, and the motion of thepiston is substantially uniform in the vicinity of the graph indicatedby the reference numeral 45. However, when the groove 31 engages theball 33 at the point 46, further retraction of the piston is prohibiteduntil the temperature declines to T1 at the point 47. At this point, thegroove 31 snaps out of engagement with the ball 33, and the pistontravels suddenly into a retracted position to the point 48. After suchretraction, the movement of the piston may be uniform as in the regionof the graph indicated by the reference numeral 49.

The means for biasing the piston 26 into the opening 24 formed withinthe boot consists of a coil spring 50 which is disposed between an uppersurface 51 of the guide member 11 and a collar 52 of the power memberpiston 26. The collar 52 and the coil spring 50 are disposed within acavity 53 which is formed centrally of the guide member 11. Also, theguide member is threaded at the outside surface 54 thereof to permit thethermal power unit to be mounted within a switch or a valve housing andas shown in FIGURES 4 and 5, respectively.

In FIGURE 1, the collar 52 of the piston 26 is resting at a landing 55of the bore 53 such that further retractible motion of the piston isprohibited. This means that the first motion of the piston will be thesnap motion, and the piston will not move through the segments 39 and 49as shown in FIGURE 3. However, the collar 52 is not necessarilypositioned as shown and the piston could be allowed to travel smoothlyon both sides of the snap action.

In FIGURE 4, a use for the thermal power unit of this invention isillustrated. In particular, a leaf spring type switch is shown toinclude a housing 56 which has side walls 57 and a base wall 58 and acover plate 59 which is secured to the side wall 57 by a number ofconnectors 60. First and second blades 61 and 62 are originally mountedwithin slots 63 and 64 formed respectively within the side wall 57.

The blade members 61 and 62 have contacts 65 and 66 formed as shown andnormally contacting each other to complete an electrical circuit betweenthe blades 61 and 62.

A thermal power unit 67 having a cup member 68 and a guide member 69 isdisposed within an opening 70 formed within the base wall 58 of thehousing 56 and is held in position by a nut 71 which is threaded aboutthe threaded surface 72 of the guide member 69.

The thermal power unit 67 has a power member piston 73 which contactsthe lower surface 74 of the blade 62 and which serves to break theelectrical contacts 65 and 66 upon the extension thereof as described inconnection with FIGURE 1. It is apparent to those skilled in the artthat the snap action motion of the contacts 65 and 66 is desirable toprevent burning of the contacts due to arcing and the like.

A further use for the thermal power unit of this invention is shown inFIGURE 5 wherein a fluid valve housing 75 is shown to have an inlet 76and an outlet 77 and a valve member 78 which includes a valve head 79engageable with a valve seat 80 formed between the inlet and the outlet.A cap member 81 is threadedly secured to the housing by a plurality ofconnectors 82 and a coil spring 83 is disposed between the cap member 81and the valve head 79 to bias the head into a closed position.

A thermal power unit 84 similar to the unit 67 is mounted within thelower wall 85 of the inlet portion 76 similar to the mounting of theunit 67 in the wall 58 of FIGURE 4. The thermal power unit 84 has apower member piston 86 which contacts the lower surface 87 of the valvehead 79 to actuate the valve head in response to the temperature travelcharacteristics shown in FIG- URE 3. It has also been found that waterhammer in a valve of this type can be eliminated by the slow returnfeature which is described in connection with FIGURE 3.

It will, of course, be understood that other variations andmodifications may be made without departing from the spirit and scope ofthe basic principles which are set forth herein and which are covered inthe appended claims.

I claim as my invention:

1. A controlled snap acting thermal power unit comprising:

a base cup having a cavity formed therein, a thermally expansiblesubstance disposed within the cavity and a resilient diaphragm extendedacross the base cup to confine the thermally expansible substancebetween the walls of the cavity and the diaphragm,

a guide member rigidly positioned against the base cup oppositely of thediaphragm with regard to the position of the thermally expansiblesubstance,

said guide member having a guide bore formed therein, a power pistonoperably disposed within the guide bore and contacting the diaphragm,

an irregular surface portion formed in a confined region of the powerpiston,

a resilient catch means mounted at a fixed point relative to the guidemember and engaging said irregular surface portion so as to resistextensible motion of the piston, and

means biasing the piston into the guide bore and against the resilientdiaphragm.

2. A controlled snap acting thermal power unit in accordance with claim1 wherein said resilient diaphragm comprises a squeeze type bootdisposed within the cup cavity and having an opening formed centrallythereof and wherein said power piston extends through the bore and intothe boot opening for being actuated by the compression of the boot dueto confinement of the thermally expansible substance as said substanceexpands on the application of heat thereto.

3. A controlled snap acting thermal power unit in accordance with claim2 wherein said base cup and guide member each have an out-turned annularflange and wherein said resilient boot has a circumferential web andmeans are provided to sandwich the web between the flanges of the basecup and guide member and wherein the guide member has a boot facinginner surface for confining the extensible movement of the upper surfaceof the boot when the thermally expansible substance expands due to theapplication of heat thereto.

4. A controlled snap acting thermal power unit in accordance with claim1 wherein said thermally expansible substance comprises a wax pellethaving a substantial thermal wax bounce.

5. A controlled snap acting thermal power unit in accordance with claim1 wherein said irregular surface comprises a detent groove formedcircumferentially about the piston and wherein said resilient catchmeans comprises a catch mounted within the guide member and biased intoengagement with the piston groove in said bore and being retractiblefrom said guide bore upon movement of said piston so as to displace saidgroove beyond the point of mounting of said catch means.

6. A controlled snap acting thermal power unit in accordance with claim5 wherein said catch means includes a second bore formed perpendicularto and intersecting said guide bore, a detent ball bearing fitted withinsaid second bore and spring means urging the ball into said detentgroove.

7. A controlled snap acting thermal power unit in accordance with claim6 wherein the diameter of said detent ball is in substantial excess tothe diameter of the crosssection of said detent groove.

8. A controlled snap acting thermal power unit in accordance with claim7 wherein said second bore is extended from the guide bore through awall of the guide member to the outside thereof and wherein anadjustment screw is threaded within the bore to adjust the compressionof the spring means.

9. A controlled snap acting thermal power unit comprising:

a base cup having a cavity formed therein containing a thermallyexpansible substance and having an outturned flange,

a guide member having an out-turned flange,

a squeeze type boot fitted within the cavity and having a web disposedbetween the out-turned flanges ofthe cup and guide member and meanssecuring the flanges together to compress the web therebetween, saidboot and said guide member each having a piston guide opening formedcentrally therethrou-gh,

a power piston operably disposed within the guide openings of the guidemember and the boot and being extensible therefrom due to the expansionof the thermally expansible substance and the squeeze action of the bootgenerated thereby,

a catch bore formed at right angles to and intersecting the guideopening of the guide member,

a detent groove formed circum'ferentially about the piston,

a detent ball bearing disposed in the catch bore and a spring meansbiasing the ball into catch engagement with the detent groove, and

means biasing the piston into the guide openings of the guide member andthe resilient boot.

10. A controlled snap acting thermal power unit in accordance with claim9 wherein said ball is slideably fitted within said catch bore andwherein said detent groove has an axial dimension which is less than thediameter of said catch bore.

11. In combination, a leaf spring type switch having first and secondcontact blades and a housing normally supporting the blades inelectrical engagement with one another, and a snap acting thermal powerunit mounted to the housing and including:

I a base cup having a cavity formed therein containing a thermallyexpansible substance and having an outturned flange,

a guide member having an out-turned flange,

a squeeze type boot fitted within the cavity and having a web disposedbetween the out-turned flanges of the cup and guide member and meanssecuring the flanges together to compress the web therebetween, saidboot and said guide member each having a piston guide opening formedcentrally therethrough,

a power piston operably disposed within the guide openings of the guidemember and the boot and being extensible therefrom due to the expansionof the thermally expansible substance and the squeeze action of the bootgenerated thereby,

said power piston extending outwardly of the guide member and contactingone of said first and second electrical blades so as to break thecontact between the blades upon the extension of the piston from theboot,

a catch bore formed at right angles to and intersecting the guideopening of the guide member,

a detent groove formed circumferentially about the piston,

a detent ball bearing disposed in the catch bore and a spring meansbiasing the ball into catch engagement with the detent groove, and

means biasing the piston into the guide openings of the guide member andthe resilient boot.

12. In combination, a fluid control valve including a ings of the guidemember and the boot and being extensible therefrom due to the expansionof the thermally expansible substance and the squeeze action of the bootgenerated thereby,

said power piston extending outwardly of the guide member and contactingsaid valve member so as to open the valve member upon the extension ofthe piston from the foot,

a catch bore formed at right angles to and intersecting the guideopening of the guide member,

a detent groove formed circu rniferentially about the piston,

a detent ball bearing disposed in the catch bore and a spring meansbiasing the ball into catch engagement with the detent groove, and

means biasing the piston into the guide openings of the guide member andthe resilient boot.

housing having an inlet and an outlet and a valve member operablydisposed between the inlet and the outlet 15 so as to control the flowof fluid therethrough and means biasing the valve member into a closedposition, and a snap acting thermal power unit mounted to the housingReferences Cited UNITED STATES PATENTS and including:

a base cup having a cavity formed therein containing a thermallyexpansible substance and having an outtumed flange, 2,938,384 5/1960Soreng et a1 60-230 XR a guide member having an out-turned flange,299O716 7/1961 Butt s 60' 23 X a squeeze type boo-t fitted within thecavity and having 633; et a1 60 23 a Web disposed between the out-turnedflanges of 25 3:336:745 8/1967 Schwartz 6O 23 the cup and guide memberand means securing the flanges together to compress the webtherebetween, said boot and said guide member each having a piston guideopening formed centrally therethrough,

a power piston operably disposed within the guide open- MARTI-N P.SCHWADRON, Primary Examiner.

C. B. DORITY, Assistant Examiner.

